Explore the vast range of titles available.

Polymer silica nanocomposites are advanced materials with unique properties combining the advantages of an inorganic nanofiller and the organic polymer matrix, which attracted considerable interest for applications in energy conversion and storage, drug delivery, environmental remediation, and many more. However, the dispersion of the nanofiller in the polymer matrix leads to complexified nanocomposite materials whose barrier properties are altered resulting in a tortuous pathway for the transport of current, matter, and velocity. The tortuosity of these nanocomposite materials, which depends on their porosity organization, is a parameter usually challenging to quantify accurately. Therefore, the objective of this study was to develop a method to quantify the electrical tortuosity and to develop a theoretical model to accurately predict electrical tortuosity in these in-house prepared silica powder and nanocomposite membrane materials at different porosity ranges. The SBA-15 silica powder and nanocomposite membranes’ conductivity was measured with the help of impedance spectroscopy in a 1 M sodium chloride electrolyte solution from which the electrical tortuosity is quantified. The calculated tortuosity of SBA-15 silica powder was found to be well correlated to the entire range of its porosity. The plots of the tortuosity versus porosity from the Maxwell and the modified Maxwell models showed a well-fitted curve to the entire range of porosity. These theoretical models will help to give a perfect prediction of the electrical tortuosity of materials from porosity measurements, which would be a vital technique to characterize materials used in electrochemical devices and battery technology.

The use of a dumbbell void model is adequate for quantifying hydraulic tortuosity from reservoir parameters. The dumbbell model of the void space involves the alternation of filtering channels of the rock with pores (macrocapillaries) and interporeal constrictions (microcapillaries). Hydraulic tortuosity is physically explained by the expansion of the flow lines of the filtration flow in the pores and contraction in the interporeal tubules. Residual water is confined mainly to clay particles that line the pore channels. Since the residual water is immobile, it leads to a narrowing of the open area of the pores and, consequently, to a specific decrease in hydraulic tortuosity.

Naturally fractured rock mass is highly inhomogeneous and contains geological discontinuities at various length scales. Hydraulic fracture stimulation in such a medium could result in complex fracture systems instead of simple planar fractures. In this study, we carried out fully coupled multiscale numerical analysis to investigate some key coupled processes of fluid-driven fracture propagation in naturally fractured rock mass. The numerical analysis follows the concept of the synthetic rock mass (SRM) method initially developed in the discrete element method (DEM). We introduce a total of five case study examples, including fracture initiation and near wellbore tortuosity, hydraulic fracture interaction with natural fractures, multi-stage hydraulic fracturing with discrete fracture network (DFN), in-fill well fracturing and frac hits after depletion-induced stress change, and induced seismicity associated with fault reactivation. Through those case studies, we demonstrate that with an advanced numerical modeling tool, the complex fracturing associated with hydraulic fracturing in naturally fractured rock mass can be qualitatively analyzed and the extent of various uncertainties can be assessed.

As one of the prevailing energy storage systems, lithium-ion batteries (LIBs) have become an essential pillar in electric vehicles (EVs) during the past decade, contributing significantly to a carbon-neutral future. However, the complete transition to electric vehicles requires LIBs with yet higher energy and power densities. Here, we propose an effective methodology via controlled nanosheet self-assembly to prepare low-tortuosity yet high-density and high-toughness thick electrodes. By introducing a delicate densification in a three-dimensionally interconnected nanosheet network to maintain its vertical architecture, facile electron and ion transports are enabled despite their high packing density. This dense and thick electrode is capable of delivering a high volumetric capacity >1,600 mAh cm−3, with an areal capacity up to 32 mAh cm−2, which is among the best reported in the literature. The high-performance electrodes with superior mechanical and electrochemical properties demonstrated in this work provide a potentially universal methodology in designing advanced battery electrodes with versatile anisotropic properties.

The formation of surface irregularities during electrode calendering remains a critical challenge. Specifically, uncoated regions of current collectors often develop severe wrinkles while coated areas frequently exhibit undesirable corrugations. Although controlling material tension has long been considered an effective strategy to address these defects, improper tension management can paradoxically lead to foil rupture or increased wrinkling severity, both result in elevated production waste. To address that, this work first explores the connection between the front/back tension intensity and the wrinkle and corrugation of the electrode via experiments and an analytical model. Results indicated that coated area corrugations were primarily influenced by the differential tension between processing stages rather than absolute tension values. For instance, reducing tension differential from 5N to 20N led to a significant 34.2% reduction in corrugation tortuosity. However, excessively large tension differences caused linear increases in shear displacement (δ), exacerbating wrinkling in the uncoated regions. After that, a novel pre-calendering process was proposed by applying compressive loading specifically to the current collector foil via a modified upper roller. Experimental results demonstrated an optimal defect reduction was achieved with both improved surface uniformity in the uncoated collectors and reduced corrugation severity in the coated area.

Abstract As one of the important parameters affecting seepage, accurate measurement of hydraulic tortuosity is crucial. Due to the similarity between the fluid transport path and the electrical conduction path in the media, electrical tortuosity is often used as hydraulic tortuosity. However, the difference in values between hydraulic and electrical tortuosity has been fuzzy in real porous media. Here, we reconstruct sandstone’s three-dimensional (3D) digital rocks using its X-ray computed tomography (CT) slices first, then perform the simulations of hydraulic and electrical transport by finite element method to extract the path of fluid and current and compute the hydraulic and electrical tortuosity. The simulation results show that the electrical tortuosity is smaller than the hydraulic tortuosity, and the average ratio between hydraulic and electrical tortuosity is about 1.09. A visual discussion of the path confirms that the reason for the difference in the two values is that their choices of the main transport channels are different. Moreover, new functions between tortuosity and porosity are proposed for the hydraulic and electrical tortuosity based on the simulation results, respectively. Compared with the previous model, it is found that the new model has better applicability in the sandstone. Finally, the calculated tortuosity is substituted into the permeability prediction formula, and the perfect fit between the predicted and the simulated permeability indicates that the tortuosity of real rocks obtained by the simulation is reliable. These conclusions provide a reference for the study of the hydraulic and electrical tortuosity of real rocks and rocks with different lithologies.

Increasing the energy density of lithium-sulfur batteries necessitates the maximization of their areal capacity, calling for thick electrodes with high sulfur loading and content. However, traditional thick electrodes often lead to sluggish ion transfer kinetics as well as decreased electronic conductivity and mechanical stability, leading to their thickness-dependent electrochemical performance. Here, free-standing and low-tortuosity N, O co-doped wood-like carbon frameworks decorated with carbon nanotubes forest (WLC-CNTs) are synthesized and used as host for enabling scalable high-performance Li-sulfur batteries. EIS-symmetric cell examinations demonstrate that the ionic resistance and charge-transfer resistance per unit electro-active surface area of S@WLC-CNTs do not change with the variation of thickness, allowing the thickness-independent electrochemical performance of Li-S batteries. With a thickness of up to 1200 µm and sulfur loading of 52.4 mg cm −2 , the electrode displays a capacity of 692 mAh g −1 after 100 cycles at 0.1 C with a low E/S ratio of 6. Moreover, the WLC-CNTs framework can also be used as a host for lithium to suppress dendrite growth. With these specific lithiophilic and sulfiphilic features, Li-S full cells were assembled and exhibited long cycling stability. Improving the energy density of lithium-sulfur batteries is necessary for their practical application. Here, the authors report free-standing and low-tortuosity carbon frameworks as host for sulfur and lithium, enabling scalable thickness independent electrochemical performance.

Pervious concrete is considered to be porous concrete because of its pore structure and excellent permeability. In general, larger porosity will increase the permeability coefficient, but will significantly decrease the compressive strength. The effects of water-cement ratio, fiber types, and fiber content on the permeability coefficient, porosity, compressive strength, and flexural strength were investigated. The pore tortuosity of the pervious concrete was determined by volumetric analysis and two-dimensional cross-sectional image analysis. The concept and calculation method of porosity tortuosity were further proposed. Results show that the permeability coefficient of the pervious concrete is the most suitable with a water-cement ratio of 0.30; the water permeability of the pervious concrete is influenced by fiber diameter. The permeability coefficient of pervious concrete with polypropylene thick fiber (PPTF) is greater than that with copper coated steel fiber (CCF) and the polypropylene fiber (PPF). The permeability coefficient is related to tortuosity and porosity, but when porosity is the same, the permeability coefficient may be different. Finally, general relations between the permeability coefficient and porosity tortuosity are constructed.

Tortuous arteries and veins are commonly observed in humans and animals. While mild tortuosity is asymptomatic, severe tortuosity can lead to ischemic attack in distal organs. Clinical observations have linked tortuous arteries and veins with aging, atherosclerosis, hypertension, genetic defects and diabetes mellitus. However, the mechanisms of their formation and development are poorly understood. This review summarizes the current clinical and biomechanical studies on the initiation, development and treatment of tortuous blood vessels. We submit a new hypothesis that mechanical instability and remodeling could be mechanisms for the initiation and development of these tortuous vessels.

Aims This study investigates the association between retinal vascular tortuosity and retinal vasculitis. Methods A retrospective review of medical records was conducted for 135 patients diagnosed with retinal vasculitis at our institution from June 2022 to June 2024. The presence and type of retinal vascular tortuosity were assessed, and logistic regression analysis was used to evaluate associations with viral infections, autoimmune conditions, and other clinical features. Results Of 256 patients with posterior uveitis, 135 patients were identified with retinal vasculitis, and 37 (27.4%) exhibited retinal vascular tortuosity. Specifically, 24 patients presented with arterial tortuosity, 5 with venous tortuosity, and 8 with both arterial and venous tortuosity. Logistic regression analysis revealed that arterial tortuosity was significantly associated with posterior synechiae, while venous tortuosity was primarily observed in patients with birdshot chorioretinopathy. Combined arterial and venous tortuosity was more commonly observed in patients with viral infections, toxoplasmosis, or psoriasis. Notably, after inflammation was controlled, retinal vascular tortuosity improved. However, the average recovery times varied between arterial tortuosity, venous tortuosity, and the combination of both. Conclusion Retinal vascular tortuosity is prevalent in retinal vasculitis and is associated with specific infectious etiologies and clinical features. It may serve as a prognostic marker for disease severity and treatment planning.